Electric heating hot plate



NOV. 23, 1965 ALEXANDER 3,219,800

ELECTRIC HEATING HOT PLATE Filed Jan. 28, 1963 IN VEN TOR.

Danda' a/ezazzdev HIS ATTORNEY United States Patent 3,219,800 ELECTRIC HEATING HOT PLATE Donald F. Alexander, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Deiaware Filed Jan. 28, 1963, Ser. No. 254,107 Claims. (Cl. 219-446) This invention relates to a domestic appliance and more particularly to an improved cooking unit for an electric range.

In order for an electric range to compete more effectively with the speed available in a gas burner, the electrical cooking unit is provided with means to over-energize the resistance coil thereof for a short period of time in order to increase the temperature of the unit rapidly. Although such over-energization does produce a rapid in crease in cooking unit temperature, the heat output of the resistance coil must overcome the insulating effect of the dielectric material in which it is compacted. This invention is directed to an arrangement for providing extra heat immediately adjacent to the cooking utensil.

Accordingly, it is an object of this invention to supply current directly to a metallic sheath of a tubular sheathed heating element.

Another object of this invention is to flash an electrical heating element by over-energizing the internal resistance coil and at the same time energizing the external metallic sheath of the heating element.

Another object of this invention is to combine a metallic ring in combination with a conventional tubular sheathed heating element, said metallic ring being selectively energized to provide a period of additional heat input.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein preferred embodiments of the present invention are clearly shown.

In the drawing:

FIGURE 1 is a top view of a tubular sheathed heating element having a portion broken away and electrically controlled in accordance with one embodiment of this invention;

FIGURE 2 is a schematic representation of this invention; and

FIGURE 3 is a top view of another embodiment of this invention.

With reference to FIGURE 1, a coiled tubular sheathed cooking unit is illustrated which is suitable for use in the top of an electric range. The tubular sheathed cooking unit 10 is comprised of an outer tubular metallic sheath 12 which encloses a coiled resistance element 14 and is separated therefrom by a compact dielectric material 16, such as magnesium oxide. It is conventional to provide a switching control 18 in a domestic power supply L N, L to selectively control the energization of the resistance coil 14. Such a control 18 could be of the infinite heat type shown in the patent to Vogelsberg 2,623,137, issued December 23, 1952. The control 18 may also be provided with conventional means to flash the resistance coil 14 on high voltage for a predetermined period of over-energization to secure a rapid heat-up of the cooking unit such as taught in the patent to Vogelsberg 2,666,124, issued January 12, 1954.

This invention is directed to an improved arrangement for initially rapidly bringing a tubular sheathed cooking unit up to cooking temperatures and contemplates utilizing the metallic sheath 12 as a high resistance heating element itself in addition to the usual internal heating from the flashed resistance coil. It should be apparent that heat transfer from the exposed bare sheath to the cooking utensil is not retarded by the insulation effects of the dielectric material 16 which surrounds the resistance ele- 3,219,800 Patented Nov. 23, 1965 ment 14. For this purpose, the secondary of a transformer 22 is connected as at 24 and 26 to the opposite ends of the metallic sheath. The secondary of the trans former is controlled to provide low voltage, say 24 volts, to eliminate shock hazard from the exposed sheath. In this way, the sheath itself acts as an auxiliary resistance element to speed up the process of heating a load from a cold start. It should be understood, however, that a partial flashing or rapid heat-up could be accomplished by energizing only the outer metallic sheath without overenergizing the resistance coil.

Turning now to FIGURE 3, another embodiment of this invention is illustrated. In this arrangement, a conventional tubular sheathed heating element 30 is adapted to be energized in the conventional manner as taught in the aforementioned Vogelsberg patents. In addition to the heating element, this invention contemplates surrounding the element 30 with a metallic ring 32 which can be selectively energized at low voltage through a transformer 34 whenever a rapid heat-up switch 36 is closed. Since this ring is in a low voltage high current circuit, the outer ring may be uninsulated electrically for rapid heat transfer without impairing the need for safety. Voltages from 5 to 25 volts A.C. have been found satisfactory for this purpose. The switch 36 can be operated manually or it can be operated automatically for a timed start to heat up rapidly a cold unit or to accelerate the heating of a cold load. Although the switch 36 is shown in the primary of the transformer to switch a minimum current, it may also be placed in the secondary circuit of the transformer, if desired.

It should now be seen that an improved arrangement has been shown for increasing the flashing ability of an electrical heating element suitable for use as a cooking unit on a domestic electric range.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A cooking unit for a domestic range adapted to support a domestic cooking utensil and comprising an electrically conductive sheath, a resistance element in said sheath and a dielectric material separating said element from said sheath, means for electrically over-energizing said resistance element to produce a first amount of additional heat to heat rapidly said cooking unit, and means for electrically directly energizing said conductive sheath to produce a second amount of additional heat to heat rapidly said cooking utensil, said last named means including a transformer having the secondary thereof in circuit with said conductive sheath.

2. A cooking unit for a domestic range comprising an electrically conductive sheath, a resistance element in said sheath and a dielectric material separating said element from said sheath, means for electrically over-energizing said resistance element to produce a first amount of additional heat to heat rapidly said cooking unit, and means for electrically directly energizing said conductive sheath to produce a second amount of additional heat to heat rapidly said cooking unit, said last named means including a transformer having the secondary thereof in circuit with said conductive sheath.

3. A heating unit adapted to support a cooking utensil thereon and comprising an electrically uninsulated cond-uctive component and an electrically energizable resistance element electrically separate from said conductive component, both of said conductive component and said resistance element being in heat transfer relationship to a cooking utensil supported on said heating unit, relatively high voltage domestic power supply means for electrically energizing said resistance element to produce a first amount of heat at said heating unit, and relatively low voltage power supply means for electrically energizing said conductive component for a limited period during heat-up to produce an additional amount of heat at said heating unit, said last named means including a transformer having the secondary thereof in circuit with said conductive component and adapted to supply power at approximately twenty-five volts or less to eliminate shock hazard from said conductive component.

4. A heating unit adapted to heat an object and comprising an electrically uninsulated conductive component and an electrically energizeable resistance element electrically separate from said conductive component, both of said conductive component and said resistance element being in heat transfer relationship to an object being heated by said heating unit, relatively high voltage domestic power supply means for electrically energizing said resistance element to produce a first amount of heat at said heating unit, relatively low voltage power supply and means for electrically energizing said conductive component for a limited period during heat-up to produce an additional amount of heat at said heating unit, said relatively low voltage power supply means including means connected to said conductive component and controllable to provide a sufiiciently low voltage to said conductive component to eliminate shock hazard therefrom.

5. A cooking unit for a domestic range adapted to support a domestic cooking utensil and comprising a coiled tubular sheathed heating element having a resistance element therein, an electrically uninsulated conductive ring surrounding said heating element in the plane thereof and electrically separate from said heating element, relatively high voltage domestic power supply means for electrically energizing said resistance element to produce a first amount of heat, and means for electrically directly energizing said conductive ring for a limited period during heat-up to produce a second amount of heat, said last named means including a transformer having the secondary thereof in circuit with said conductive ring and adapted to supply power at approximately twenty-five volts or less to eliminate shock hazard from said conductive ring.

References (Tited by the Examiner UNITED STATES PATENTS 2,207,871 7/1940 Myers 219 446 2,419,083 4/1947 Myers 219-446 2,678,991 5/1954 Amfitheatrof 219464 2,804,535 8/1957 Tuttie 219-433 2,971,077 2/1961 Palmer 219436 RICHARD M. WOOD, Primary Examiner.

Notice of Adverse Decision in Interference In Interference No. 95,955 involving Patent No. 3,219,800, D. F. Alexander, ELECTRIC HEATING HOT PLATE, final judgment adverse to the patentee was rendered July 22, 1968, as to claims 1 and 2.

[Ofieial Gazette September 24, 1.968.] 

1. A COOKING UNIT FOR A DOMESTIC RANGE ADAPTED TO SUPPORT A DOMESTIC COOKING UNTENSIL AND COMPRISING AN ELECTRICALLY CONDUCTIVE SHEATH, A RESISTANCE ELEMENT IN SAID SHEATH AND DIELECTRIC MATERIAL SEPARATING SAID ELEMENT FROM SAID SHEATH, MEANS FOR ELECTRICALLY OVER-ENERGIZING SAID RESISTANCE ELEMENT TO PRODUCE A FIRST AMOUNT OF ADDITIONAL HEAT TO HEAT RAPIDLY SAID COOKING UNIT, AND MEANS FOR ELECTRICALLY DIRECTLY ENERGIZING SAID CONDUCTIVE SHEATH TO PRODUCE A SECOND AMOUNT OF ADDITIONAL HEAT TO HEAT RAPIDLY SAID COOKING UTENSIL, SAID LAST NAMED MEANS INCLUDING A TRANSFORMER HAVING THE SECONDARY THEREOF IN CIRCUIT WITH SAID CONDUCTIVE SHEATH. 